Heretofore, as a medical device that is used to acquire a diagnostic image to diagnose, for example, a lesion area in the living body, there is a diagnostic imaging catheter that is used in an imaging apparatus for diagnosis using, for example, intravascular ultrasound (IVUS) or optical coherence tomography (OCT).
The diagnostic imaging catheter is equipped with a drive shaft, which is provided with a transmitting and receiving unit that transmits and receives inspection waves, and a sheath, into which the drive shaft is inserted in such a manner as to be movable forward and backward. During the use of the diagnostic imaging catheter, what is called a pullback operation (an inward pulling operation) is performed which moves the drive shaft from a distal side to a proximal side by moving the drive shaft backward while rotating the drive shaft, or a push-in operation is performed which pushes the drive shaft into the distal side (refer to Japanese Patent Application Publication No. 2015-119994).
When the diagnostic imaging catheter is used, the inside of the sheath is filled with a priming liquid such as a physiological salt solution (a priming process) so as to efficiently transmit and receive inspection waves. To fill the inside of the sheath with the priming liquid, a syringe is usually connected to a port provided at a hub on the hand side, and the priming liquid is injected into the sheath. Then, the injected priming liquid flows toward the distal side through a gap between the sheath and the drive shaft and is thus discharged from a communicating hole provided at the distal end of the sheath to the outside of the catheter.
The pushing force necessary on the syringe to inject the priming liquid depends on the flow path resistance in a flow path through which the priming liquid flows. In other words, as the flow path resistance is larger, a larger pushing force is required on the syringe. Therefore, in order to smoothly perform the priming process, it is desirable to reduce the flow path resistance. Here, the flow path resistance is inversely proportionate to the diameter of the flow path through which the priming liquid flows and is proportionate to the length of the flow path through which the priming liquid flows.
While examples of the method for reducing the flow path resistance include increasing a gap (flow path diameter) between the sheath and the drive shaft, increasing the gap may cause the vibration of the transmitting and receiving unit occurring during the rotation of the drive shaft to become large, so that an image may not be able to be appropriately acquired.
Based upon the above, a diagnostic imaging catheter is needed which allows the priming process to be smoothly performed by reducing the flow path resistance without increasing the gap between the sheath and the drive shaft.
In relation to this, for example, Japanese Patent Application Publication No. 2000-083959 discloses a diagnostic imaging catheter in which a priming port is provided at a unit connector (corresponding to a sheath connector) provided at the distal side of a hub (corresponding to a drive shaft connector). According to the diagnostic imaging catheter disclosed therein, since the length of a flow path through which a priming liquid flows is shorter than that in a diagnostic imaging catheter in which the port is provided at the hub, the flow path resistance can be reduced.
However, with respect to a diagnostic imaging catheter according to Japanese Patent Application Publication No. 2000-083959, in order to smoothly perform a priming process, a further reduction of the flow path resistance is demanded.
One consideration though, is that if the priming liquid directly contacts the drive shaft during the priming process, the drive shaft may be, for example, deformed or damaged, so that an image may not be able to be appropriately acquired.
In view of the above-mentioned problems, the disclosure herein provides a diagnostic imaging catheter which allows a priming process to be smoothly performed by reducing the flow path resistance without increasing a gap between the sheath and the drive shaft, while preventing a priming liquid from contacting the drive shaft to disable appropriately acquiring an image.